1. Technical Field
The present invention relates to a MEMS element and a manufacturing method therefor, in particular, to an optical modulator and a manufacturing method therefor.
2. Description of the Related Art
A MEMS refers to a micro electro mechanical system, and is fabricated by a MEMS technology that forms a three dimensional structure on a silicon substrate by means of a semiconductor manufacturing process. Such a MEMS has been applied in diverse fields including optics. Through the MEMS technology can be produced optical components smaller than 1 mm, by which micro optical systems are realized. These optical components including optical modulators, micro-lenses, and the like have been widely applied in telecommunication devices, displays, and recording devices due to such advantages as quick response time, low level of loss, and convenience in layering and digitalizing.
The optical modulator is a device in which a signal-controlled element is used to modulate a beam of light. The optical modulator can be divided mainly into a direct type directly controlling the on/off state of light, and an indirect type exploiting optical reflection and diffraction. The indirect type can be further divided into an electrostatic type and a piezoelectric type according to its operation style.
Regardless of its operation style, the indirect type optical modulator performs optical modulations by means of optical interference occurring due to the pathlength difference between diffracted lights. Especially, the piezoelectric type optical modulator generates the pathlength difference by using driving power of piezoelectric elements, which contract and expand according to the voltage applied thereto (for further understanding, refer to the description regarding FIGS. 3 and 4). Therefore, the piezoelectric elements play an important role in the piezoelectric type optical modulator.
However, during the manufacturing process for the optical modulator, moisture permeates into the optical modulator, thereby changing the operational characteristics of the piezoelectric elements. Such changes in the piezoelectric elements cause the gap between ribbons and an insulation layer in the optical modulator to fluctuate, thereby deteriorating the optical diffraction properties and the reliability of the optical modulator.